Locking and safety device for electric switches



E. BASSANI 3,018,341

LOCKING AND SAFETY DEVICE FOR ELECTRIC SWITCHES Jan. 23, 1962 Filed Feb. 9

United States PatentO 3,018,341 LOCKING AND SAFETY DEVICE FOR ELECTRIC SWITCHES Ermanno Bassani, Milan, Italy, assignor to Societa per Azioni Bassani, Milan, Italy, an Italian joint-stock company Filed Feb. 9, 1959, Ser. No. 792,191 Claims priority, application Italy Feb. 10, 1958 Claims. (Cl. 200-50) This invention relates to' a lock and safety device for electric switches. According to the invention the handle or other actuating member is locked during removal of protective arrangements or other safety devices in order to positively prevent actuation of the switches, in case they are not insulated against the voltage carrying members.

Referring particularly, but not exclusively,- to the switches as used in low and middle voltage electrical instauations, it is' well known that such switches are manufactured so that all metal members be duly protected, and that, should the protection be removed, the switches must first be locked.

' This is also the case when the switches are fitted with safety devices, as for instance fuses,- overc'urre'nt relays and the'like.

In addition, the replacement or r'e-c alibrat'ion of the" above members must be made after disconnection of the switches, to prevent possible accidents.

The maiiipurpose of the invention is the provision of a device which" can be fitted on electric switches in general, and particularly on switches of the enclosed and protected type, to cause the movable members thereof to be positively locked, when the safety devices, or in general the casings within which such switches are fitted, are to be removed, or opened. u p

A further purpose of the invention is to allow the fuses to be replaced, or the relays or the like to be calibrated, without any danger of accident, whereas when voltage is carried by the different members, the access thereto is positively prevented.

According to the invention movable contact pieces are actuated by a swinging or cross-member characterized, in that said swinging member is provided with at least one pawl cooperating with an associated spring arm secured to the switch. At least one cover or like protective member in which the enclosed switch metal members are therewith engaged, whereby when removing the cover the spring arm is released, thus locking the swinging member by which the switch is actuated.

Moreover, locking means are formed on the pawl securedto the switch actuating member. Such means engage, when the switch is closed, with at least a portion of the cover to prevent opening thereof, thus shutting oif access to all voltage carrying members.

It is to be understood that the invention extends also to switches (being such general term inclusive of all devices provided not only for breaking and making a circuit, but also for switching-over, shunting and reversing purposes).

Other objects and features of the invention will become apparent from the following detailed description of a preferred embodiment thereof, as applied to a conventional switch.

In the drawings:

FIG. 1 is a perspective view of a switch adapted for replacement of the fuses.

FIG. 2 shows the device of FIG. 1 with the switch cover removed.

FIG. 3 is a partly cut-away view of the switch.

FIG. 4 is a cross-section view along the line IVIV of FIG. 3.

FIG. 5 is a perspective view of a detail.

The switch consists of a box or enclosure 10, provided with a cover- 12 secured thereto by the nuts 14. The members of said switch are fitted, in known manner, on a small supporting block 16, preferably made of ceramic materials secured inside the box.

In greater detail, said block is fitted with one or more pairs of suitably shaped spring contacts 18 and 20, which are provided with the associated terminals 22 and 24' and which cooperate with a contact roller 26, kept in place by a small plate 28, which is under the action of the spring means (not shown); Such plate and its spring are seated into asuitable opening, formed on a cross member 32, provided on both ends with pins 34, which are secured on suitable supports, formed in the block 16. Thus, the rollers 26 can be brought into two positions, i.e. one in which they engage with the ends of spring contacts (circuit making) and another in which they are wholly disengaged therefrom (circuit breaking).

The contact 20 is also formed with a clamp-shaped extension 25 to engage with one end of a fuse 36, whose opposite end is secured in known manner-, as for instance by a cap 38 made of insulating material, on a plate' 40, whereon a terminal 42 is also secured. Saidcross member 32 is provided with an actuating handle 35, that comes out of the cover through a suitable opening; further openings are also provided for the caps 38 of fuses'36, whereby said fuses can be replaced from the outside of the box without having recourse to removal of the cover.

According to this invention, radial extensions 44 are formed on both ends of cross member 32,- near the pins 34; a plate 46', secured to said extensions has a hookshaped extension 48, two dogs 50 and 52 beingformedon the outer end thereof.

Each one of said hooks 48 engages in a slit 54 out near one end of a spring arm 56, secured to a small bracket58, fastened to the inside wall of box- 10'. This arm, which extends with its longitudinal axis at a right angle to the rotation axis of cross member 32, consists of a spring plate, shaped in such a manner as to urge said arm in the direction of arrow X in FIG. 4, i.e. toward the cover 12.

Said cover 12 is provided with a countercover 60, that extends on the area of the openings through which the fuse caps 38 project out of cover, and is provided with arms 62, connected by the hinges 64 to said cover, said countercover being removably secured to cover 12 by means of threaded nut 66. Thus the caps 38 of fuses are made inaccessible by said countercover, which on the other hand is provided with holes or windows 68 for the visual check of the condition of the fuses.

The countercover 60 is box-shaped, thus leaving a suitable space for the caps 38 by which the fuses 36 are kept in position, and in addition countercover 60 is provided with spring tongues to keep spare fuses 36'.

Stirrups 70 are secured to countercover 60, opposite to ends of arm 62. These stirrups can be extended beyond the cover 12, through the openings 72, out of which extend also the hooks 48.

When the countercover 60 is in its closed position, the

dog 50 of hook 48 engages with the end 74 of each stirrup 70. Moreover, as clearly shown by FIG. 4, the end 74 of each stirrup 70 abuts with its lower face against the end of the spring arm 56, whereby this latter, when the countercover 60 is kept against the cover 12, is forced in a direction opposite to that of arrow X.

Under such conditions, it is to be understood that the cross member 32 (FIG. 1) may be caused to swing around the pins 34, whereby the switch can be actuated in the usual manner.

None of the voltage carrying members, as for instance the terminals 22, 24 and 42 and the fuses 36 are accessible, since neither the cover 12 nor the countercover 60 can be removed, when the switch is closed, by loosening the screws 14 and 66. In fact, even after loosening of said screws, both the cover 12 and the countercover 60 are kept fastened to box by the dogs 50 of hooks 48. The switch must be switched oil to allow lifting of the cover 60 and consequent access to cap 38 of fuses 36, Le. the cross member 32 is to be swung in a clockwise di rection (see FIG. 4), thus disengaging the dogs 50 of hooks 48 from stirrups 70. Then, the countercover can be lifted by swinging it around its hinges 64, whereupon the cover 12 can be removed from box 10 by loosening the screws 14.

As shown in the FIG. 2, the switch output terminals 42 are made accessible by the removal of cover 12, whereas the input terminals are covered by a plate 78 made of an insulating material.

It will be understood that after lifting of countercover 60 or removal of cover 12, the switch cannot be further actuated, since while lifting the countercover 60 or removing the cover 12, each spring arm 56, by virtue of its elasticity, is moved in the direction of arrow X, and the ends of slit 54 thereof will engage with the dogs 52, whereby preventing any swinging in counterclockwise direction of cross member 32, which is thus locked, whereby the circuit cannot be closed. The circuit can be then closed only after lowering of the arms 56, and this operation can be carried out only after bringing back the cover 12 and the countercover 60 to their original places.

In the manner as above described, all accidental contacts can be always positively prevented, even when burnt fuses are to be replaced.

Many modifications and changes may be made in the above described device, according to the construction and operational features of the switch in which the invention is to be embodied.

What is claimed is:

1. A switch comprising a base, spaced contacts on said base, a pivotal member on said base and adapted to connect said contacts, at least one electrical component on said base in operative association with said contacts, a

hooked member on said pivotal member and having an outer end, two dogs on said outer end, a spring on said base and provided with an opening accommodating the passage of said dogs, a cover shielding said component, and a stirrup on said cover and engaged by one of said dogs for locking the cover on said base,- said stirrup bearing, under the influence of said one dog, against said spring and maintaining the latter in a position whereby unimpeded movement of said hooked member and pivotal member is permitted with the cover in position, said spring assuming, upon removal of said cover and release'by said stirrup, a position of interference with the other of said dogs to prevent movement of the pivotal member and a resulting actuation of the switch with the cover removed.

2. A switch as claimed in claim 1, wherein said cover includes a first section engaging said base and having open ings respectively accommodating said stirrup and exposing said component, and a second section hinged on said first section, the second section pivotally supporting said stirrup.

3. A switch as claimed in claim 2, comprising locking means for fixing said second section on said first section and said first section on said base.

4. A switch as claimed in claim 2, wherein one of said contacts includes a U-shaped bracket portion detachably engaging said component.

5. A switch as claimed in claim 2, wherein said pivotal member includes a roller adapted to couple said contacts electrically.

References Cited in the file of this patent UNITED STATES PATENTS 2,007,911 Von Normann July 9, 1935 2,239,105 Kingdon Apr. 22, 1941 2,332,633 Green Oct. 26, 1943 2,954,444 Jones et a1 Sept. 27, 1960 FOREIGN PATENTS 734,845 Great Britain Aug. 10, 1955 

